We are proposing a fifteen year follow-up study of boys with attention deficit hyperactivity disorder (ADHD). At a baseline assessment, we ascertained 140 ADHD and 120 normal control children from psychiatric and non-psychiatric settings. These groups had 454 and 368 first degree biological relatives, respectively. We have followed the probands and their siblings at one, four and ten year follow-ups. Over 90% of the subjects ascertained at baseline were re-examined at each follow-up assessment. We now propose a five-year study that will re-examine the probands and siblings into adulthood, fifteen years after the baseline assessment. We have five main Aims: 1) To assess the persistence, normalization of functioning and remission in ADHD children and their siblings; 2) To assess the predictive validity of comorbidity with psychiatric disorders and neuropsychological and social dysfunction; 3) To evaluate the validity of DSM-IV subtypes of ADHD; 4) To assess the Psychometric Features of the Adult ADHD diagnosis; and 5) To assess how gene variants will predict adult outcome. In our preliminary work, we have begun to address each of the Specific Aims that are the focus of the proposed work. We view the proposed extension of our work as an essential step for several reasons. First, although there have been seven follow-up studies of ADHD children and only two (our included) used DSM-III-R criteria. Moreover, unlike most prior follow-up studies, the proposed work can comprehensively address psychiatric comobidity in ADHD because we did not use comorbid conditions to exclude cases at baseline and we assessed for a wide range of comorbid conditions at each assessment. Only a few prior studies assessed intelligence, achievement and school functioning, none have thoroughly examined attentional-executive neuropsychological functions and only one examined psychosocial and family functioning. In contrast, our study has taken a multidimensional approach to measurement; we have assessed these domains of functioning at baseline and each follow-up assessment. Because the treatment interventions used in our sample are not being controlled, we will be able to document to naturalistic course of treatment use. Also, we are the only long-term study to collect clinical and molecular genetic data on all first degree relatives and to follow the siblings of ADHD and control subjects into adulthood. For these reasons, we expect the proposed work to clarify the course and outcome of ADHD.